Deck 19: Principles of Chemical Reactivity: Entropy and Free Energy

Question 1

Which of the following linear chain alcohols is likely to have the highest standard entropy in the liquid state?

A) CH₃OH
B) CH₃CH₂OH
C) CH₃CH₂CH₂OH
D) CH₃CH₂CH₂CH₂OH
E) CH₃CH₂CH₂CH₂CH₂OH

Answer 1

CH₃CH₂CH₂CH₂CH₂OH

Question 2

Which of the following statements concerning entropy is not correct?

A) The entropy of a system increases as the number of available microstates increases.
B) The entropy of a system is proportional to the natural log of the number of microstates.
C) In a spontaneous process, ΔS(universe) indicates the extent to which energy is dispersed.
D) The dispersal of matter, such as the spontaneous expansion of a gas, cannot be explained by an increase in entropy.
E) Entropy is a measure of the extent of energy dispersal.

Answer 2

The dispersal of matter, such as the spontaneous expansion of a gas, cannot be explained by an increase in entropy.

Question 3

Which of the following represents the change in entropy for a system going from 142 possible microstates to 830 possible microstates? (k = 1.381 × 10^-23 J/K)

A) $1.61 \times 10 ^ { - 22 }$ J/K
B) $9.02 \times 10 ^ { - 23 }$ J/K
C) ? $9.02 \times 10 ^ { - 23 }$ J/K
D) $2.44 \times 10 ^ { - 23 }$ J/K
E) ? $2.44 \times 10 ^ { - 23 }$ J/K

Answer 3

$2.44 \times 10 ^ { - 23 }$ J/K

Question 4

Which of the following compounds has the highest standard entropy per mole at 298 K?

A) H₂O(l)
B) CaCO₃(s)
C) CO(g)
D) SiO₂(s)
E) CH₃OH(l)

Question 5

For a certain reversible process, q = 88.06 kJ at 29.4°C. Which of the following is the ΔS for the process?

A) 0.291 J/K
B) 291 J/K
C) 3.00 J/K
D) -0.291 J/K
E) 2590 J/K

Question 6

What is the S0 for ozone if the standard entropy change for the reaction below is 411 J/K⋅mol-rxn and S⁰[O₂(g)] = 205 J/K⋅mol. 6 O₃(g) → 9 O₂(g)

A) 364 J/K⋅mol-rxn
B) 478 J/K⋅mol-rxn
C) 239 J/K⋅mol-rxn
D) −117 J/K⋅mol-rxn
E) −59 J/K⋅mol-rxn

Question 7

If a chemical reaction occurs in a direction that has a positive change in entropy, then _____.

A) the change in enthalpy must be negative.
B) the reaction must be spontaneous.
C) the heat goes from the system into the surroundings.
D) the reaction must be exothermic.
E) the disorder of the system increases.

Question 8

Use the given thermodynamic data and the reaction below to calculate ?S°(universe) for the formation of Fe2O3(s) at 298.15 K. 3 Fe(s) + 2 O₂(g) ? Fe₃O₄(s)
$$\begin{array} { l l l } \text { Species } & \Delta _f H ^ { \circ } ( \mathrm { kJ } / \mathrm { mol } ) & S ^ { \circ } ( \mathrm { J } / \mathrm { K } \cdot \mathrm { mol } ) \\\hline \mathrm { Fe } ( \mathrm { s } ) & 0.0 & 27.8 \\\mathrm { O } _ { 2 } ( \mathrm {~g} ) & 0.0 & 205.1 \\\mathrm { Fe } _ { 3 } \mathrm { O } _ { 4 } ( \mathrm {~s} ) & - 1118.4 & 146.4\end{array}$$

A) -3404 J/K
B) -1162 J/K
C) +561.2 J/K
D) +3404 J/K
E) +7639 J/K

Question 9

Calculate the standard entropy change for the following reaction: 2 SO₂(g) + O₂(g) → 2 SO₃(g)
Given: S°[SO₂(g)] = 248.2 J/K⋅mol, S°[O₂(g)] = 205.1 J/K⋅mol, and S°[SO₃(g)] = 256.8 J/K⋅mol.

A) -196.5 J/K·mol-rxn
B) -94.0 J/K·mol-rxn
C) -187.9 J/K·mol-rxn
D) +187.9 J/K·mol-rxn
E) +196.5 J/K·mol-rxn

Question 10

The standard entropy for the formation of sulfur hexafluoride from the sulfur and fluorine is -348.7 J/K ⋅mol-rxn at 298.15 K. What is the standard molar entropy of sulfur hexafluoride for the reaction below? (Given: S°[S(s)] = 32.1 J/K ⋅mol and S°[F2(g)] = 202.8 J/K ⋅mol)

A) -988.6 J/K⋅mol
B) +291.8 J/K⋅mol
C) -291.8 J/K⋅mol
D) -113.2 J/K⋅mol
E) +113.8 J/K⋅mol

Question 11

What is the standard entropy change for the following reaction?
$$\begin{array} { l l l l l } & 4 \mathrm {~N} _ { 2 } ( \mathrm {~g} ) & + 12 \mathrm { H } _ { 2 } ( \mathrm {~g} ) & \rightarrow & 8 \mathrm { NH } _ { 3 } ( \mathrm {~g} ) \\\\S _ { 298 } ^ { 0 } & 191.5 & 130.6 && 192.3\end{array}$$ (J/mol?K)

A) -794.8 J/K?mol-rxn
B) 794.8 J/K?mol-rxn
C) 2948.8 J/K?mol-rxn
D) -2948.8 J/K?mol-rxn
E) -129.8 J/K?mol-rxn

Question 12

Which of the following is the first law of thermodynamics?

A) In a spontaneous process, the entropy of the universe increases.
B) There is no disorder in a perfect crystal at 0 K.
C) The total energy of the universe is always decreasing.
D) Energy cannot be created or destroyed.
E) mass and energy are conserved in all chemical reactions.

Question 13

Which of the following is true of the deposition of a gaseous substance?

A) ΔS° = 0 and ΔH° = 0.
B) ΔS° > 0 and ΔH° > 0.
C) ΔS° < 0 and ΔH° > 0.
D) ΔS° < 0 and ΔH° < 0.
E) ΔS° > 0 and ΔH° < 0.

Question 14

In which of the following reactions is Δ_rS° expected to be positive?

A) 2C₂H₆(g) + 7O₂(g) → 4CO₂(g) + 6H₂O(l)
B) Ga(l) → Ga(s)
C) H₂O(l) + 2SO₂(g) → H₂SO₄(l)
D) CO₂(g) → CO₂(s)
E) None of these

Question 15

For the reaction Br₂(l) → 2Br(g), _____.

A) ΔH is + and ΔS is +
B) ΔH is + and ΔS = 0
C) ΔH is - and ΔS is -
D) ΔH is - and ΔS is +
E) ΔH is + and ΔS is -

Question 16

Calculate ΔS°(universe) for the combustion of acetylene at 298.15 K using the reaction below. (Given: ΔS°(system) = -194.6 J/K and ΔH°(system) = -2511.2 kJ) 2 C₂H₂(g) + 5 O₂(g) → 4 CO₂(g) + 2 H₂O(g)

A) -2453.2 J/K
B) -186.2 J/K
C) +186.2 J/K
D) +1290.4 J/K
E) +8228.0 J/K

Question 17

Which of the following is the second law of thermodynamics?

A) In a spontaneous process, the entropy of the universe increases.
B) There is no disorder in a perfect crystal at 0 K.
C) The total energy of the universe is always increasing.
D) The total energy of the universe is constant.
E) Mass and energy are conserved in all chemical reactions.

Question 18

Which of the following is the third law of thermodynamics as defined by Ludwig Boltzmann?

A) A perfect crystal at 0 K has zero entropy.
B) In a spontaneous process, the entropy of the universe increases.
C) The total entropy of the universe is always increasing.
D) The total mass of the universe is constant.
E) Mass and energy are conserved in all chemical reactions.

Question 19

Which of the following changes lead to a decrease in entropy?

A) Sugar dissolving in coffee
B) Diffusion of perfume throughout a room
C) Evaporation of gasoline
D) The sublimation (vaporization) of dry ice (solid carbon dioxide)
E) Condensation of steam on glass

Question 20

For which of the following reactions will the entropy of a system decrease?

A) 2 NH₃(g) → N₂(g) + 3 H₂(g)
B) 2 C(s) + O₂(g) → 2 CO(g)
C) CaCO₃(s) → CaO(s) + CO₂(g)
D) 2 NO₂(g) → N₂O₄(g)
E) NaOH(s) → Na⁺(aq) + OH^-(aq)

Question 21

What is the sign of ΔH (system) and ΔS (system) if a chemical reaction is spontaneous only at lower temperatures under standard conditions?

A) ΔH (system) is negative, and ΔS (system) is negative.
B) ΔH (system) is positive, and ΔS (system) is positive.
C) ΔH (system) is positive, and ΔS (system) is negative.
D) ΔH (system) is negative, and ΔS (system) is positive.
E) None of these

Question 22

When a real gas is compressed from low pressure to high pressure, its temperature increases. Which of the following is true for ΔH and ΔS?

A) ΔH < 0 and ΔS < 0
B) ΔH < 0 and ΔS > 0
C) ΔH > 0 and ΔS < 0
D) ΔH > 0 and ΔS > 0
E) ΔH < 0 and ΔS = 0

Question 23

Calculate ΔG° at 298 K for the reaction below. I₂(g) + Br₂(g) → 2IBr(g)
Given: Δ_rH° = -11.6 kJ/mol-rxn; Δ_rS° = 12 J/K⋅mol-rxn at 298 K.

A) -8.02 kJ/mol-rxn
B) 15.2 kJ/mol-rxn
C) -15.2 kJ/mol-rxn
D) 3.59 × 10³ kJ/mol-rxn
E) -3.59 × 10³ kJ/mol-rxn

Question 24

A change of state occurring in a system is accompanied by 60.7 kJ of heat that is transferred to the surroundings at a constant pressure and at a constant temperature of 300 K. Calculate the ΔS(surroundings) for the process.

A) -202 J/K
B) -60.7 kJ/K
C) 202 J/K
D) 60.7 kJ/K
E) 239 kJ/K

Question 25

If a cube of ice at 0 °C is placed outside on a warm summer day, the ice will melt spontaneously. What are the signs of Δ_rH, Δ_rS, and Δ_rG for the process?

A) Δ_rH < 0, Δ_rS > 0, and Δ_rG < 0
B) Δ_rH < 0, Δ_rS < 0, and Δ_rG < 0
C) Δ_rH < 0, Δ_rS > 0, and Δ_rG > 0
D) Δ_rH > 0, Δ_rS > 0, and Δ_rG < 0
E) Δ_rH > 0, Δ_rS < 0, and Δ_rG > 0

Question 26

For a chemical reaction, if Δ_rG° = 0, then _____.

A) K > 0
B) K = 0
C) K < 0
D) K > 1
E) K = 1

Question 27

Which of the following is correct for the condensation of gaseous oxygen at -188 °C? (The normal boiling point of oxygen is -183 °C.)

A) ΔH < 0, ΔS > 0, and ΔG > 0.
B) ΔH < 0, ΔS < 0, and ΔG >0.
C) ΔH > 0, ΔS < 0, and ΔG < 0.
D) ΔH = 0, ΔS = 0, and ΔG < 0.
E) ΔH > 0, ΔS > 0, and ΔG > 0.

Question 28

For the reaction given below, ?H⁰ = -1516 kJ at 25°C and ?S⁰ = -432.8 J/K at 25°C. This reaction is spontaneous _____.
SiH₄(g) + 2 O₂(g) ?SiO₂(s) + 2 H₂O $( \ell )$

A) only below a certain temperature
B) only above a certain temperature
C) at all temperatures
D) only when entropy is zero
E) None of these

Question 29

At what temperatures will a reaction be spontaneous if Δ_rH° = +117 kJ and Δ_rS° = -35 J/K?

A) All temperatures below 94.1 K
B) Temperatures between 12.7 K and 135 K
C) All temperatures above 94.1 K
D) The reaction will be spontaneous at any temperature.
E) The reaction will never be spontaneous.

Question 30

While diluting concentrated sulfuric acid with water, the temperature of the solution increases rapidly. What are the signs of ΔrH, ΔrS, and ΔrG for the process?

A) Δ_rH < 0, Δ_rS > 0, and Δ_rG < 0
B) Δ_rH < 0, Δ_rS < 0, and Δ_rG < 0
C) Δ_rH < 0, Δ_rS > 0, and Δ_rG > 0
D) Δ_rH > 0, Δ_rS > 0, and Δ_rG < 0
E) Δ_rH > 0, Δ_rS < 0, and Δ_rG > 0

Question 31

At what temperatures will a reaction be spontaneous if Δ_rH° = +62.4 kJ and Δ_rS° = +301 J/K?

A) All temperatures below 207 K
B) All temperatures above 207 K
C) Temperatures between 179 K and 235 K
D) The reaction will be spontaneous at any temperature
E) The reaction will never be spontaneous

Question 32

Which of the following is true of a reaction that is product-favored?

A) Q < K and $\Delta$ _rG < 0
B) Q < K and $\Delta$ _rG > 0
C) Q = K and $\Delta$ _rG = 0
D) Q > K and $\Delta$ _rG < 0
E) Q > K and $\Delta$ _rG > 0

Question 33

ΔG° = 0 for a reaction indicates that _____.

A) the reaction favors formation of products
B) the reaction is at equilibrium
C) the reaction is nonspontaneous
D) the reaction is spontaneous
E) the reaction cannot reach equilibrium

Question 34

The dissolution of ammonium nitrate occurs spontaneously in water at 25 °C. As ammonium nitrate dissolves, the temperature of the water decreases. What are the signs of Δ_rH, Δ_rS, and Δ_rG for this process?

A) Δ_rH > 0, Δ_rS < 0, and Δ_rG > 0
B) Δ_rH > 0, Δ_rS > 0, and Δ_rG > 0
C) Δ_rH > 0, Δ_rS > 0, and Δ_rG < 0
D) Δ_rH < 0, Δ_rS < 0, and Δ_rG < 0
E) Δ_rH < 0, Δ_rS > 0, and Δ_rG > 0

Question 35

A 100 mL sample of water is placed in a coffee cup calorimeter. When 1.0 g of an ionic solid is added, the temperature decreases from 21.5 °C to 20.8 °C as the solid dissolves. For the dissolving of the solid, _____.

A) ΔH < 0
B) ΔS(universe) > 0
C) ΔS(system) < 0
D) ΔS(surroundings) > 0
E) None of these

Question 36

If Δ_rG° > 0 for a reaction at all temperatures, then Δ_rH° is _____ and Δ_rS° is _____.

A) Negative; positive
B) Positive; negative
C) Negative; negative
D) Positive; positive
E) Positive; either positive or negative

Question 37

A flask containing helium gas is released into a closed room. Which of the following ideas concerning entropy is/are true?

A) ΔS(system) > 0
B) Matter is dispersed.
C) ΔS(universe) > 0
D) This process is spontaneous.
E) All of these statements are true.

Question 38

Hydrogen gas is prepared by electrolysis of water according to the reaction below. 2 H₂O( $\ell$ ) ? 2 H₂(g) + O₂(g)
Predict the signs of ?_rH and ?_rS.

A) ?_rH > 0 and ?_rS > 0
B) ?_rH < 0 and ?_rS > 0
C) ?_rH > 0 and ?_rS < 0
D) ?_rH < 0 and ?_rS < 0
E) ?_rH = 0 and ?_rS < 0

Question 39

For a reaction, Δ_rH° = -208.8 kJ and Δ_rS° = -308.2 J/K. At what temperature will Δ_rG° = 0.00 kJ?

A) 0.68 K
B) 677.5 K
C) 1476 K
D) 6435 K
E) 0.85 K

Question 40

If a chemical reaction is exothermic but not spontaneous, which of the following must be true?

A) Δ_rG > 0, Δ_rS > 0, and Δ_rH > 0
B) Δ_rG < 0, Δ_rS > 0, and Δ_rH > 0
C) Δ_rG > 0, Δ_rS < 0, and Δ_rH > 0
D) Δ_rG < 0, Δ_rS < 0, and Δ_rH < 0
E) Δ_rG > 0, Δ_rS < 0, and Δ_rH < 0

Question 41

Given the following and that R = 8.314 J/K ?mol, determine the equilibrium constant, K, at 298K for the following reaction:
AgBr(s) ? Ag⁺(aq) + Br-(aq)
$\begin{array}{ll}\text { Substance } & \underline{\Delta}_{\mathrm{f}} \mathrm{G}^{\circ}(\mathrm{kJ} / \mathrm{mol}) \text { at } 298 \mathrm{~K} \\\hline\mathrm{Br}-(\mathrm{aq}) & -104.0 \\\mathrm{Ag}^{+}(\mathrm{aq}) & 77.12 \\\mathrm{AgBr}(\mathrm{s}) & -96.9\end{array}$

A) $5.3 \times 10 ^ { - 13 }$
B) $5.2 \times 10 ^ { 4 }$
C) $1.9 \times 10 ^ { 12 }$
D) $1.9 \times 10 ^ { - 5 }$
E) $1.8 \times 10 ^ { - 49 }$

Question 42

Calculate Δ_rG° for the reaction below at 25.0 °C. CH₄(g) + H₂O(g) → 3 H₂(g) + CO(g)
Given: Δ_fG° [CH₄(g)] = -50.8 kJ/mol, Δ_fG° [H₂O(g)] = -228.6 kJ/mol, Δ_fG° [H₂(g)] = 0.0 kJ/mol, and Δ_fG° [CO(g)] = -137.2 kJ/mol.

A) -416.3 kJ/mol-rxn
B) -142.2 kJ/mol-rxn
C) +142.2 kJ/mol-rxn
D) +315.0 kJ/mol-rxn
E) +416.3 kJ/mol-rxn

Question 43

What is the equilibrium constant for reaction below at 25 °C? (R = 8.314 J/K?mol) 2 NO(g) + O₂(g) $\leftrightharpoons$ 2 NO₂(g); ?_fG° [NO(g)] = +86.6 kJ/mol and ?_fG° [NO₂(g)] = +51.2 kJ/mol.

A) 3.9 × 10^-13
B) 1.0 × 10-¹¹
C) 2.6 × 10¹²
D) 1.6 × 10⁶
E) 3.8 × 10²⁸

Question 44

For a chemical system, Δ_rG° and Δ_rG are equal when:

A) the system is in equilibrium.
B) the reactants and products are in standard state conditions.
C) the equilibrium constant, K, equals 0.
D) the reaction quotient, Q, is less than 1.
E) the reactants and products are in the gas phase.

Question 45

For which of the following substances is the standard free energy of formation not equal to zero at 298 K?

A) Xe(g)
B) Sn(s)
C) N₂(g)
D) Mg(g)
E) Mn(s)

Question 46

Using the given data, determine ?rG° at 500.0 K for the reaction below.
Ba(s) + H₂O(g) ? BaO(s) + H₂(g)
$$\begin{array} { l l l } \underline { \text { Substance } } & \Delta _ { f } \underline { H ^ { \circ } ( \mathrm { kJ } / \text { mol-rxn } ) \text { at } 298 \mathrm {~K} } &{ S ^ { \circ } ( \mathrm { J } / \mathrm { K } \cdot \text { mol-rxn } ) \text { at } 298 \mathrm {~K} } \\\hline\mathrm{Ba}(s) & 0 & 62.8 \\\mathrm{H}_{2} \mathrm{O}(g) & -241.8 & 188.7 \\\mathrm{BaO}(s) & -592 & 70.4 \\\mathrm{H}_{2}(g) & 0 & 130.6\end{array}$$

A) 325.0 kJ/mol-rxn
B) -325.0 kJ/mol-rxn
C) 335.2 kJ/mol-rxn
D) -335.2 kJ/mol-rxn
E) -375.5 kJ/mol-rxn

Question 47

Calculate ?_rG° for the reaction below at 425 °C, 2 HI(g) $\leftrightharpoons$ H₂(g) + I₂(g); K = 0.018. (R = 8.314 J/K?mol)

A) 6.12 × 10³ kJ/mol-rxn
B) 1.05 × 10⁴ kJ/mol-rxn
C) 1.42 × 10⁴ kJ/mol-rxn
D) 2.33 × 10⁴ kJ/mol-rxn
E) 3.34 × 10⁵ kJ/mol-rxn

Question 48

The K_sp of silver bromide is 5.4 × 10-¹³ at 298 K. AgBr(s) $\leftrightharpoons$ Ag⁺(aq) + Br-(aq)
What is ?_rG°? (R = 8.314 J/K?mol)

A) -3.0 × 10¹ kJ/mol
B) -5.87 kJ/mol
C) 5.87 kJ/mol
D) 3.0 × 10¹ kJ/mol
E) 7.0 × 10¹ kJ/mol

Question 49

Determine ?_fG° at 298 K for SnO using the data below.
Sn(s) + SnO₂(s) ? 2SnO(s)
Given: $\Delta _ { \mathrm { r } } G ^ { \circ } = 12.0 \mathrm {~kJ} / \mathrm { mol } - \mathrm { rxn }$ at $298 \mathrm {~K}$
Substance $\quad \Delta f G ^ { \circ } ( \mathrm { kJ } / \mathrm { mol } )$ at $298 \mathrm {~K}$
$\mathrm { SnO } ( s ) \quad\quad\quad ?$
$\mathrm { SnO } _ { 2 } ( s ) \quad - 515.8$

A) -251.9 kJ/mol
B) -503.8 kJ/mol
C) 527.8 kJ/mol
D) 263.9 kJ/mol
E) 1055.6 kJ/mol

Question 50

Thermodynamics can be used to determine all of the following except _____.

A) the temperature at which a reaction is spontaneous
B) the extent to which a reaction occurs
C) the direction in which a reaction is spontaneous
D) the rate of reaction
E) the entropy change of a reaction

Question 51

The standard free energy change for a chemical reaction is +13.3 kJ/mol. Which of the following is the equilibrium constant for the reaction at 125 °C? (R = 8.314 J/K⋅mol)

A) 2.8 × 10^-6
B) 2.0 × 10^-5
C) 4.7 × 10^-3
D) 1.8 × 10^-2
E) 2.1 × 10²

Question 52

Calculate ?_rG° at 25.0 °C for the reaction below. 2 Na(s) + 2 H₂O( $\ell$ ) ? 2 NaOH(aq) + H₂(g)
Given: ?_rH° = -366.6 kJ/mol-rxn and ?_rS° = -154.2 J/K?mol-rxn.

A) -371.2 kJ/mol-rxn
B) -320.6 kJ/mol-rxn
C) -215.4 kJ/mol-rxn
D) +371.2 kJ/mol-rxn
E) +4634.9 kJ/mol-rxn

Question 53

Which of the following relationships is not true?

A) $\Delta G _ { \text {sys } } ^ { \circ } = \Delta H _ { \text {sys } } ^ { \circ } - T \Delta S _ { \text {sys } } ^ { \circ }$
B) $\Delta G _ { \text {sys } } ^ { \circ } = - R T \ln ( K )$
C) $\Delta S _ { \text {univ } } ^ { \circ} = \Delta S _ { \text {sys } } ^ { \circ } + \Delta S _ { \text {surr } } ^ { \circ }$
D) $\Delta H = \Delta H _ { \text {sys }}^{\circ} + R T \ln ( K )$
E) $\Delta G _ { \text {sys } } ^ { \circ } = - T \Delta S _ { \text {univ } } ^ { \circ }$

Question 54

Which of the following is the equilibrium constant for the reaction below at 25 °C? (R = 8.314 J/K ⋅mol) MgCO3(s) MgO(s) + CO2(g); ΔfG° [MgCO3(s)] = -1028.2 kJ/mol, ΔfG [MgO(s)] = -568.8 kJ/mol, and ΔfG° [CO2(g)] = -394.4 kJ/mol.

A) 4.0 × 10^-12
B) 0.97
C) 1.0
D) 1.0 × 10⁴
E) 2.5 × 10¹¹

Question 55

Using the given data, determine ?rG° at 298 K for the precipitation reaction below.
Ag⁺(aq) +Br?(aq) ? AgBr(s)
$\begin{array}{ll}\text { Substance } & \Delta f \mathrm{G}^{\circ}(\mathrm{kJ} / \mathrm{mol}) \text { at } 298 \mathrm{~K} \\\hline\mathrm{Br}-(\mathrm{aq}) & -104.0 \\\mathrm{Ag}^{+}(\mathrm{aq}) & 77.12 \\\mathrm{AgBr}(\mathrm{s}) & -96.9\end{array}$

A) -70.0 kJ/mol-rxn
B) -123.8 kJ/mol-rxn
C) 70.0 kJ/mol-rxn
D) 123.8 kJ/mol-rxn
E) 84.2 kJ/mol-rxn

Question 56

The standard free energy change associated with the dissolution of ammonium nitrate in water is -6.73 kJ/mol at 298.15 K. NH₄NO₃(s) $\leftrightharpoons$ NH₄NO₃(aq)
Which of the following is the equilibrium constant for the reaction? (R = 8.314 J/K?mol)

A) 1.9 × 10^-3
B) 6.6 × 10^-2
C) 1.0
D) 15
E) 5.2 × 10²

Question 57

Estimate the boiling point of ethanol, C₂H₅OH, using the given the following thermodynamic parameters. $$\begin{array} { l l l } & \mathrm { C } _ { 2 } \mathrm { H } _ { 5 } \mathrm { OH }(\ell)& \mathrm { C } _ { 2 } \mathrm { H } _ { 5 } \mathrm { OH } ( \mathrm { g } ) \\\hline \Delta _ { f } H ^ { \circ } ( \mathrm { kJ } / \mathrm { mol } ) & - 277.0 & - 235.3 \\S ^ { \circ } ( \mathrm { J } / \mathrm { K } \cdot \mathrm { mol } ) & 160.7 & 282.7 \\\Delta _ { f } G ^ { \circ } ( \mathrm { kJ } / \mathrm { mol } ) & - 174.7 & - 168.5\end{array}$$

A) 22 °C
B) 44 °C
C) 61 °C
D) 69 °C
E) 91 °C

Question 58

Given the following data: S(g) + O₂(g) → SO₂(g)
Δ_rG° = -300.1 kJ/mol-rxn
2 S(g) + 3 O₂(g) → 2 SO₃(g)
Δ_rG° = -742.1 kJ/mol-rxn
Calculate Δ_fG° for the reaction below.
SO₂(g) + 1/2 O₂(g) → SO₃(g)

A) -1042.2 kJ/mol-rxn
B) -71.0 kJ/mol-rxn
C) +2.47 kJ/mol-rxn
D) +71.0 kJ/mol-rxn
E) +1042.2 kJ/mol-rxn

Question 59

The standard free energy of formation of AgI(s) is -66.2 kJ/mol. Δ_rG° for the reaction 2AgI(s) → 2Ag(s) + I₂(s) is:

A) 132.4 kJ
B) 66.2 kJ
C) -132.4 kJ
D) -66.2 kJ
E) 800 KJ

Question 60

What is the equilibrium constant for the reaction below at 298 K?
2C(s) + 3H₂(g) ? C₂H₆(g)
Given: ?_rH° = -84.68 kJ; ?_rS° = -173.8 J/K at 298 K. (R = 8.314 J/K?mol)

A) 5.8 × 10⁵
B) 1.0 × 10?5
C) 8.6 × 10^-10
D) 1.7 × 10^-6
E) 7.0 × 10¹⁴

Question 61

At a temperature (in kelvin units) of _____, the entropy of a pure crystal is 0.0 J/K.

Question 62

Which of the following statements about entropy is true?

A) The entropy of a substance will increase on going from a solid to a liquid to a gas.
B) The entropy of any substance increases as the temperature is lowered.
C) The entropy of a gas is independent of the volume of the gas.
D) The entropy of a gas decreases with an increase in volume.
E) The entropy of a substance increases with a decrease in the number of moles.

Question 63

Does the formation of complex molecules such as proteins and nucleic acids from more simple molecules contradict the second law of thermodynamics?

Question 64

_____ changes only occur in the direction that leads toward chemical equilibrium.

Question 65

In any chemical process, energy must be conserved. This is the _____ law of thermodynamics.

Question 66

For any process, the change in entropy of the universe equals the sum of the entropy changes for the system and for the ________.

Question 67

The change in entropy for any process is not dependent upon the pathway by which the process occurs. In other words, the change in entropy for any process is a(n) _____ function.

Question 68

The total entropy of the universe is always increasing. This is a statement of the _____ law of thermodynamics.

Question 69

Calculate the enthalpy of vaporization of water at its normal boiling point. ΔS° [H₂O( )] = 69.9 J/K⋅mol and ΔS° [H₂O(g)] = 188.8 J/K⋅mol.

Question 70

A reaction is said to be under thermodynamic control when _____.

A) thermodynamics is controlling the ratio of products
B) the ratio of products is the same at all temperatures
C) thermodynamics is controlling the speed of the reaction
D) the ratio of reactants is equal to the ratio of products
E) there are both acidic and basic reactants in a reaction